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TitleTree-ring nitrogen isotopes reflect anthropogenic NOX emissions and climatic effects
AuthorSavard, M M; Bégin, C; Smirnoff, A; Marion, J; Rioux-Paquette, E
SourceEnvironmental Science & Technology (ES & T) vol. 43, no. 3, 2009 p. 604-609,
Alt SeriesEarth Sciences Sector, Contribution Series 20100308
PublisherAmerican Chemical Society (ACS)
Mediapaper; on-line; digital
File formatpdf
Subjectsenvironmental geology; environmental analysis; environmental studies; environmental impacts; pollution; pollutants; vegetation; stable isotope studies; isotopes; hydrogen isotopes; carbon isotopes; oxygen isotopes; climate effects; climate; nitrogen isotopes
ProgramEnvironment and Health
ProgramMetals in the Environment (MITE)
AbstractAnthropogenic emissions of atmospheric nitrogen have increased over the last century, but the monitoring of nitrous oxide concentrations is only recent. Can trees from temperate regions be used to infer past changes in nitrogen cycles? To consider this question, we investigate nitrogen isotope (delta15N) ring series from pine and beech trees near Montre´al, and beech specimens of Georgian Bay Islands. The delta15N values show coherent intertree and interspecies trends, independent of the sapwood-heartwood transition zones, implying that these results reflect local environmental conditions. At both sites, shortterm isotopic fluctuations correlate directly with precipitation and inversely with temperature. Long-term isotope decreases of 1.5 to 2permil suggest progressive changes in soil nitrogen after 1951. In Georgian Bay, an additional important change is inferred on the basis of a 1.5permil increase initiated after 1971. At both sites, long-term series correlate with a proxy for NOx emissions. We propose that the contrasted long-term delta15N changes of Montreal and Georgian Bay reflect deposition of NOx emissions from cars and coal-power plants, with higher proportions from coal burning in Georgian Bay. This research suggests that tree-ring delta15N series may record both, regional climatic conditions and anthropogenic perturbations of N cycles.